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Biomedical subjects

Hubert Labelle

Publications and source records attributed to Hubert Labelle.

At least 37 records · Page 2Linked to original sources
PubMed2005

Complete bilateral agenesis of the ilium in a 7-year-old ambulatory girl: case report.

STUDY DESIGN: A 7-year-old ambulatory girl with complete bilateral agenesis of the ilium is reported. OBJECTIVE: To document the clinical evolution and the spino-pelvic balance of a girl with bilateral agenesis of the ilium. SUMMARY OF BACKGROUND DATA: Scapuloiliac dysostosis is a rare focal skeletal dysplasia consisting in hypoplasia of ilium and scapula. METHODS: A 7-year-old girl with a short stature was referred to our clinic at 35 months of age for an asymptomatic lumbar hyperlordosis. She presented a waddling gait, and normal range of motion of her upper and lower limbs. The neurologic examination was within normal limits. RESULTS: Initial radiographs at 35 months of age showed complete bilateral agenesis of the ilium with preservation of the pubis, ischium, and sacrum, associated with a bilateral high hip dislocation. The lumbar lordosis and sacral slope were 89 degrees and 84 degrees, respectively. A radiographic skeletal survey also showed hypoplasia of both scapulae. At 7 years old, the girl was fully ambulatory, with a waddling gait and had no pain. The sacral slope and lumbar lordosis have increased to 97 degrees and 97 degrees, respectively. There was no evidence of spondylolisthesis. So far, the patient has required no treatment for her condition. CONCLUSION: This article reports a unique case of scapuloiliac dysostosis with complete bilateral agenesis of the ilium in an ambulatory girl. This case indicates that a functional gait is possible with bilateral congenital absence of the ilium, provided that there is adequate muscular support and normal neurologic function.

Child↗
PubMed2005

The importance of spino-pelvic balance in L5-s1 developmental spondylolisthesis: a review of pertinent radiologic measurements.

STUDY DESIGN: A review article. OBJECTIVES: The purpose of this article is to review pertinent radiologic measurements for the evaluation of spino-pelvic balance in developmental spondylolisthesis, based on the experience of the Spinal Deformity Study Group. SUMMARY OF BACKGROUND DATA: Over the past decade, pelvic morphology has been shown to significantly influence spino-pelvic balance of the human trunk in normal and pathologic conditions. This finding has important implications for the evaluation and treatment of developmental spondylolisthesis and has fostered a renewed interest in the radiologic evaluation of spino-pelvic balance in this condition. METHODS: The lateral standing radiographs of the spine and pelvis of subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence, sacral slope, pelvic tilt, L5 incidence angle, lumbosacral angle, lumbar lordosis, thoracic kyphosis, and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of an adult and child reference population. RESULTS: The pelvic shape, best quantified by the pelvic incidence angle, determines the position of the sacral endplate. The spine reacts to this position by adapting through lumbar lordosis, the amount of lordosis increasing as the sacral slope increases in order to balance the trunk in the upright position. Pelvic incidence, sacral slope, pelvic tilt, and lumbar lordosis are found to be significantly greater in subjects with developmental spondylolisthesis, while thoracic kyphosis is significantly lower when compared to a reference population. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases, suggesting that pelvic anatomy has a direct influence on the development of a spondylolisthesis. Studies also indicate that pelvic incidence is unaffected by surgical reduction and instrumentation. Pelvic tilt, sacral slope, and thoracic kyphosis are slightly affected, while grade, L5 incidence angle, lumbosacral angle, and shape of the lumbar spine are significantly improved after surgery. A postoperative improvement in L5 incidence angle and lumbosacral angle appears correlated with a better outcome while subjects with a poor outcome have a higher preoperative grade. CONCLUSIONS: Spino-pelvic balance in the sagittal plane can be considered as an open linear chain linking the head to the pelvis where the shape and orientation of each successive anatomic segment are closely related and influence the adjacent segment. Pelvic morphology and spino-pelvic balance are abnormal in developmental spondylolisthesis. These abnormalities should be quantified on lateral standing radiographs of the spine and pelvis and have important implications for the evaluation and treatment of this pathologic condition.

Humans↗
PubMed2005

Biomechanical simulations of scoliotic spine correction due to prone position and anaesthesia prior to surgical instrumentation.

BACKGROUND: The positioning of patients during scoliosis surgery has been shown to affect the scoliosis curve, yet positioning has not been exploited to help improve surgical outcome from a biomechanics point of view. Biomechanical models have been used to study other aspects of scoliosis. The goal of this study is to simulate the specific influence of the prone operative position and anaesthesia using a finite element model with patient personalized material properties. METHODS: A finite element model of the spine, ribcage and pelvis was created from the 3D standing geometry of two patients. To this model various positions were simulated. Initially the left and right supine pre-operative bending were simulated. Using a Box-Benkin experimental design the material properties of the intervertebral disks were personalized so that the bending simulations best matched the bending X-rays. The prone position was then simulated by applying the appropriate boundary conditions and gravity loads and the 3D geometry was compared to the X-rays taken intra-operatively. Finally an anaesthesia factor was added to the model to relax all the soft tissues. FINDINGS: The behaviour of the model improved for all three positions once the material properties were personalized. By incorporating an anaesthesia factor the results of the prone intra-operative simulation better matched the prone intra-operative X-ray. However, the anaesthesia factor was different for both patients. For the prone position simulation with anaesthesia patient 1 corrected from 62 degrees to 47 degrees and 43 degrees to 31 degrees. Patient 2 corrected from 70 degrees to 55 degrees and 40 degrees to 32 degrees for the thoracic and lumbar curves respectively. INTERPRETATION: Positioning of the patient, as well as anaesthesia, provide significant correction of the spinal deformity even before surgical instrumentation is fixed to the vertebra. The biomechanical effect of positioning should be taken into consideration by surgeons and possibly modify the support cushions accordingly to maximise 3D curve correction. The positioning is an important step that should not be overlooked by when simulating surgical correction and biomechanical models could be used to help determine optimal cushion placement.

Adolescent↗
PubMed2005

Analysis of the sagittal balance of the spine and pelvis using shape and orientation parameters.

OBJECTIVE: The purpose of this study is to introduce a method to analyze and characterize the global sagittal balance of the human trunk using indexes derived from the shape and orientation of the pelvis and cervical, thoracic, and lumbar spine. METHODS: Standing lateral x-rays of a cohort of 160 asymptomatic young adult volunteers were obtained. On each radiograph, a simplified model of the spine and pelvis was created using a dedicated computer software, and the following shape and orientation variables were calculated at each anatomic level: pelvic incidence, pelvic tilt, sacral slope, cervical curvature and tilt, thoracic curvature and tilt, and lumbar curvature and tilt. RESULTS: Significant linear correlations were found between each single adjacent shape parameter as well as between each single adjacent orientation parameter at all anatomic levels. Significant correlations were also found between some shape and orientation parameters at the same anatomic level as well as between adjacent anatomic areas. In general, the linear correlations were stronger between shape and orientation variables at the pelvic, lumbar, and cervical areas and weaker at the thoracic level and between the thoracic and lumbar areas. CONCLUSIONS: These results confirm that the pelvis and spine in the sagittal plane can be considered as a linear chain linking the head to the pelvis where the shape and orientation of each anatomic segment are closely related and influence the adjacent segment to maintain a stable posture with a minimum of energy expenditure. Changes in shape or orientation at one level will have a direct influence on the adjacent segment. Knowledge of these normal relationships is of prime importance for the comprehension of sagittal balance in normal and pathologic conditions of the spine and pelvis.

Adult↗
PubMed2005

A hierarchical statistical modeling approach for the unsupervised 3-D biplanar reconstruction of the scoliotic spine.

This paper presents a new and accurate three-dimensional (3-D) reconstruction technique for the scoliotic spine from a pair of planar and conventional (postero-anterior with normal incidence and lateral) calibrated radiographic images. The proposed model uses a priori hierarchical global knowledge, both on the geometric structure of the whole spine and of each vertebra. More precisely, it relies on the specification of two 3-D statistical templates. The first, a rough geometric template on which rigid admissible deformations are defined, is used to ensure a crude registration of the whole spine. An accurate 3-D reconstruction is then performed for each vertebra by a second template on which nonlinear admissible global, as well as local deformations, are defined. Global deformations are modeled using a statistical modal analysis of the pathological deformations observed on a representative scoliotic vertebra population. Local deformations are represented by a first-order Markov process. This unsupervised coarse-to-fine 3-D reconstruction procedure leads to two separate minimization procedures efficiently solved in our application with evolutionary stochastic optimization algorithms. In this context, we compare the results obtained with a classical genetic algorithm (GA) and a recent Exploration Selection (ES) technique. This latter optimization method with the proposed 3-D reconstruction model, is tested on several pairs of biplanar radiographic images with scoliotic deformities. The experiments reported in this paper demonstrate that the discussed method is comparable in terms of accuracy with the classical computed-tomography-scan technique while being unsupervised and while requiring only two radiographic images and a lower amount of radiation for the patient.

Algorithms↗
PubMed2004

Vertebral wedging characteristic changes in scoliotic spines.

STUDY DESIGN: A morphometric analysis of vertebral wedging in vertebrae from scoliotic specimens. OBJECTIVE: To quantify the vertebral body changes in 30 anatomic specimens affected by a scoliotic deformity. SUMMARY OF BACKGROUND DATA: Only a few studies have evaluated the exact changes occurring at the level of the vertebral body in scoliotic spines. Most are observational studies of rare scoliotic specimens presenting major curvatures. The orientation of vertebral wedging is important for the planning of corrective surgery, performing vertebral osteotomy, and the evaluation of possible growth modulation. MATERIALS AND METHODS: Thirty scoliotic specimens with curves presenting various degrees of severity were studied using a three-dimensional digitizing protocol developed to create a precise three-dimensional reconstruction of the vertebrae. Every scoliotic specimen was then matched with a normal specimen, and comparisons were made on the vertebral body parameters both for thoracic and lumbar vertebrae. Analysis of variance and t test calculations were performed to identify significant differences with P = 0.05. RESULTS: A total of 471 vertebrae from scoliotic spines and 510 vertebrae from normal specimens were measured. Vertebral wedging increased progressively towards the apex of the curve and was maximal at the apex. Vertebral wedging was more prominent in the frontal plane, and there was minimal wedging in the sagittal plane. Vertebral heights were significantly different at T3 and T4 for the upper adjacent curve and at T6-T8 for a typical right thoracic curve, with smaller heights located on the concavity of the curve. No changes were observed on the convexity of the curve. CONCLUSION: Vertebral wedging is an essential component of the scoliotic deformity. The present study provides critical information for corrective surgery and vertebral osteotomy, as vertebral wedging occurs primarily in the frontal plane. Accurate knowledge of this deformity should also provide new insight into corrective surgical strategies aiming at growth modulation and more efficient surgical correction.

Disease Progression↗
PubMed2004

Spondylolisthesis, pelvic incidence, and spinopelvic balance: a correlation study.

STUDY DESIGN: A retrospective study of the sagittal alignment in developmental spondylolisthesis. OBJECTIVES: To investigate the role of pelvic anatomy and its effect on the global balance of the trunk in developmental spondylolisthesis. SUMMARY OF BACKGROUND DATA: Pelvic incidence (PI) is a fundamental anatomic parameter that is specific and constant for each individual, and independent of the three-dimensional orientation of the pelvis. Recent studies have suggested an association between a high PI and patients with isthmic spondylolisthesis. METHODS: The lateral standing radiographs of the spine and pelvis of 214 subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of a cohort of 160 normal subjects. Student's tests were used to compare the parameters between the curve types and Pearson's correlation coefficients were used to investigate the association between all parameters (alpha = 0.01). RESULTS: PI, SS, PT, and LL are significantly greater (P < 0.01) in subjects with spondylolisthesis, while TK is significantly decreased. PI has a direct linear correlation (0.41-0.65) with SS, PT, and LL. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases. CONCLUSIONS: Since PI is a constant anatomic pelvic variable specific to each individual and strongly determines SS, PT, and LL, which are position-dependent variables, this study suggests that pelvic anatomy has a direct influence on the development of a spondylolisthesis.Study participants with an increased pelvic incidence appear to be at higher risk of presenting a spondylolisthesis, and an increased PI may be an important factor predisposing to progression in developmental spondylolisthesis.

Adolescent↗
PubMed2004

Melatonin signaling dysfunction in adolescent idiopathic scoliosis.

STUDY DESIGN: In vitro assays were performed with bone-forming cells isolated from 41 patients with adolescent idiopathic scoliosis and 17 control patients exhibiting another type of scoliosis or none. OBJECTIVE: To determine whether a dysfunction of the melatonin-signaling pathway in tissues targeted by this hormone is involved in adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Pinealectomy in chicken has led to the formation of a scoliotic deformity, thereby suggesting that a melatonin deficiency may be at the source of adolescent idiopathic scoliosis. However, the relevance of melatonin in the etiopathogenesis of that condition is controversial because most studies have reported no significant change in circulating levels of melatonin in patients with adolescent idiopathic scoliosis. METHODS: Primary osteoblast cultures prepared from bone specimens obtained intraoperatively during spine surgeries were used to test the ability of melatonin and Gpp(NH)p, a GTP analogue, to block cAMP accumulation induced by forskolin. In parallel, melatonin receptor and Gi protein functions were evaluated by immunohistochemistry and by coimmunoprecipitation experiments. RESULTS: The cAMP assays demonstrated that melatonin signaling was impaired in osteoblasts isolated from adolescent idiopathic scoliosis patients to different degrees allowing their classification in 3 distinct groups based on their responsiveness to melatonin or Gpp(NH)p. CONCLUSION: Melatonin signaling is clearly impaired in osteoblasts of all patients with adolescent idiopathic scoliosis tested. Classification of patients with adolescent idiopathic scoliosis in 3 groups based on functional in vitro assays suggests the presence of distinct mutations interfering with the melatonin signal transduction. Posttranslational modifications affecting Gi protein function, such as serine residues phosphorylation, should be considered as one possible mechanism in the etiopathogenesis of AIS.

Adenylyl Cyclases↗
PubMed2004

Sagittal alignment of the spine and pelvis during growth.

STUDY DESIGN: Prospective study of the sagittal plane alignment of the spine and pelvis in the normal pediatric population. OBJECTIVES: To document the sagittal alignment of the spine and pelvis and its change during growth in the normal pediatric population. SUMMARY OF BACKGROUND DATA: Pelvic morphology as well as sagittal alignment of the spine and pelvis in the pediatric population are poorly defined in the literature. METHODS: Five parameters were evaluated on lateral standing radiographs of 180 normal study participants 4 to 18 years of age: thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence. Statistical analysis was performed using two-tailed Student t tests and Pearson's coefficients (level of significance = 0.01). RESULTS: The mean thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence values were 43.0 degrees, 48.5 degrees, 41.2 degrees, 7.2 degrees and 48.4 degrees, respectively. There was no significant difference between males and females. Thoracic kyphosis, lumbar lordosis, pelvic tilt, and pelvic incidence were found to be weakly correlated with age, while sacral slope remained stable with growth. CONCLUSIONS: Pelvic morphology, as measured by the pelvic incidence angle, tends to increase during childhood and adolescence before stabilizing into adulthood, most likely to maintain an adequate sagittal balance in view of the physiologic and morphologic changes occurring during growth. Pelvic tilt and lumbar lordosis, two position-dependent parameters, also react by increasing with age, most likely to avoid inadequate anterior displacement of the body center of gravity. Sacral slope is achieved with the standing posture and is not further significantly influenced by age. These results are important to establish baseline values for these measurements in the pediatric population, in view of the reported association between pelvic morphology and the development of various spinal disorders such as spondylolisthesis and scoliosis.

Adolescent↗
PubMed2004

The effect of intraoperative traction during posterior spinal instrumentation and fusion for adolescent idiopathic scoliosis.

STUDY DESIGN: A retrospective study comparing patients having traction and a control group not having traction during posterior spinal instrumentation and fusion (PSIF) for adolescent idiopathic scoliosis (AIS). OBJECTIVE: To evaluate the effect of intraoperative traction on surgical correction of AIS. SUMMARY OF BACKGROUND DATA: When the Cotrel-Dubousset instrumentation system was introduced, the use of intraoperative traction was advocated. However, there is no specific report documenting the effect of intraoperative traction on the correction of AIS. METHODS: The medical and radiologic records of 140 AIS patients treated by PSIF were reviewed. Forty of these patients had intraoperative traction using a head halter associated with lower extremity skin traction. The radiologic outcome was compared between the two groups intraoperatively (before instrumentation with the first rod) and after surgery using Student t tests (level of significance = 0.05). RESULTS: The intraoperative and postoperative corrections of the coronal primary Cobb angle were similar for both groups, although the patients in the traction group had smaller preoperative Cobb angles and more flexible curves and were instrumented with more screws. The postoperative thoracic kyphosis was significantly increased in both groups. The lumbar lordosis at the 1-year follow-up was maintained in the control group, but it was significantly decreased in the traction group. CONCLUSION: The authors do not recommend the routine use of intraoperative traction using a head halter combined with skin traction for all AIS patients undergoing PSIF. However, it could be helpful in selected cases, such as in patients having pelvic obliquity and requiring instrumentation of the pelvis.

Adolescent↗
PubMed2004

Thoracic pedicle morphometry in vertebrae from scoliotic spines.

STUDY DESIGN: A morphometric analysis of thoracic pedicles in vertebrae from scoliotic specimens. OBJECTIVE: The objective of this study was to quantify the changes occurring in thoracic pedicles affected by a scoliotic deformity. SUMMARY OF BACKGROUND DATA: There exists a lot of controversy in the literature concerning the shape and size of thoracic pedicles in idiopathic scoliosis. In recent years, thoracic pedicle screws are being used more frequently in corrective spine surgery, but few studies have evaluated the morphology of scoliotic thoracic pedicles. MATERIAL AND METHOD: Thirty scoliotic specimens with curves presenting various degrees of severity were studied using a three-dimensional digitizing protocol developed to create a precise three-dimensional reconstruction of the vertebrae. Twenty-two parameters describing specifically the pedicles were then calculated for each vertebra from these reconstructions. Every scoliotic specimen was then matched with a normal specimen to provide for a representative control group and comparisons were made on pedicle width, length, height, surface, and orientation. RESULTS: A total of 683 thoracic vertebrae were measured (325 scoliotic and 358 normal vertebrae). Pedicles located on the concavity of typical right thoracic curves were found to be significantly thinner than their normal counterparts with a maximal mean difference of 1.37 mm at T8. The pedicles on the concavity of the high thoracic compensatory curve were also found to be significantly diminished with a maximal mean difference of 1.68 mm at T4. Mean left pedicle width at T8 (concavity) and mean right pedicle width at T4 (concavity) were found to be 4.08 mm and 2.60 mm, respectively. Pedicle length was found to be slightly increased, and pedicle height was found to be slightly decreased in pedicles from scoliotic spines with no preference for concavity or convexity. Pedicle orientation and inclination were unchanged with respect to each corresponding vertebral body. CONCLUSION: These results are of critical importance for clinicians performing spinal corrective surgery in patients with AIS. Pedicle width is significantly diminished on the concavity of scoliotic curves. Our results advocate caution in the use of pedicle screws in the thoracic spine especially on the concave side of the curve.

Adult↗
PubMed2004

Biomechanical evaluation of the Boston brace system for the treatment of adolescent idiopathic scoliosis: relationship between strap tension and brace interface forces.

STUDY DESIGN: Prospective study to evaluate the association between strap tension and brace interface forces in the treatment of adolescent idiopathic scoliosis using the Boston brace system. OBJECTIVES: To determine the strap tension associated with optimal brace interface forces. SUMMARY OF BACKGROUND DATA: Trim lines, pad placement, and areas of relief for the brace are guided by radiographic studies. However, optimal adjustment of strap tension is unclear and remains mostly empirical. METHODS: Brace interface forces in all regions of the trunk were measured for 41 patients with adolescent idiopathic scoliosis at three standardized strap tensions (20 N, 40 N, and 60 N). The brace interface forces were assessed using a mat made of force-sensing transducers. Equivalent interface pressure for each trunk region was also calculated to estimate the distribution of the interface forces. RESULTS: The brace interface forces and the corresponding effective areas increased along with the strap tension for all patients. For patients with a single right thoracic curve, the interface pressure tended to increase with increasing strap tension. This increase was significant in the left axillary, right thoracic, right pelvic, and sternal regions. For double right thoracic-left lumbar curves, the increase in interface pressure was significant in the left axillary, right pelvic, and sternal regions. However, most of this increase occurred between 20 N and 40 N of strap tension, with only slight increase or even a decrease in interface pressures between 40 N and 60 N. CONCLUSIONS: The strap tension should be set as high as possible (up to 60 N) for right thoracic curves. For right thoracic-left lumbar curves, the optimal strap tension was approximately 40 N. However, clinicians should ensure that the prescribed strap tension does not cause excessive skin pressure or affect the compliance with the brace. A side opening in the right lumbar area may improve the effectiveness of the brace for double right thoracic-left lumbar curves, but care must be taken to avoid skin problems at the opening.

Adolescent↗
PubMed2004

Spinal shape changes resulting from scoliotic spine surgical instrumentation expressed as intervertebral rotations and centers of rotation.

This paper reports the changes in spinal shape resulting from scoliotic spine surgical instrumentation expressed as intervertebral rotations and centers of rotation. The objective is to test the hypothesis that the type of spinal instrumentation system (Cotrel-Dubousset versus Colorado) does not influence these motion parameters. Intervertebral rotations and centers of rotation of the scoliotic spines were computed from the pre- and post-operative radiographs of 82 patients undergoing spinal correction. The three-dimensional (3D) reconstruction of six anatomical landmarks was achieved for each of the thoracic and lumbar vertebrae. A least-squares approach based on singular value decomposition was used to calculate the rigid body transformation parameters. Average centers of rotation for all intervertebral levels are located in the neural canal at the mid-sagittal plane and approximately at the superior endplate level of the inferior vertebra. Intervertebral rotations have components in all planes: 6.7 degrees (frontal), 5.5 degrees (sagittal) and 4.5 degrees (transverse) RMS for all intervertebral levels. Nearly all intervertebral rotations and centers of rotation are not significantly different for the two instrumentation systems. Various intervertebral rotations and 3D reconstruction errors were simulated on a theoretical model of a lumbar functional unit to assess the proposed method. Intervertebral rotation errors were 1.7 degrees when simulating 3D errors of 3mm on the position of the landmarks. Maximum errors for the position of centers of rotation were below 1cm in the case of intervertebral rotations larger than 2.5 degrees (most cases), but were larger (38 mm) for small intervertebral rotations (<1 degrees ). The type of instrumentation system did not influence intervertebral rotations and centers of rotation. These results provide valuable data for the development and validation of simulation models for surgical instrumentation of idiopathic scoliosis.

Adult↗
PubMed2004

Simultaneous, bilateral, and three-dimensional gait analysis of elderly people without impairments.

OBJECTIVE: The main objectives of this study were to determine if the right and left lower limbs in the gait of elderly people developed similar muscle moment and power patterns and to determine whether their associated mechanical energies were different during two consecutive gait cycles. DESIGN: A total of 18 able-bodied male subjects aged 71 +/- 6.8 yrs participated in this study. Data were collected using three Optotrak position sensors and two AMTI force platforms. RESULTS: The peak muscle powers were very similar in the sagittal plane and reflected gait symmetry, except for greater and significant differences produced by the hip extensors. Differences in the frontal and transverse planes were mainly attributed to the actions taken by the muscles, leading the lower limbs to compensate and to dynamically balance and propel the body forward during two consecutive gait cycles. In terms of mechanical energy, 13% greater positive work was done in the left limb and was associated with asymmetrical behavior of the lower limbs to propel the body forward. The total negative work was similar for both limbs, and substantial work was done in the frontal plane by the hip, indicating the role of muscle activity in this plane to control the pelvis and trunk against gravitational forces. CONCLUSIONS: In addition to the importance of a balance-control function in the gait of healthy, elderly subjects, muscle activity made an important contribution to propelling the body forward. Gait asymmetry in elderly subjects seems to be related to different degrees of energy generated by the lower limbs for the propulsion function, whereas both limbs contribute similarly to the balance-control function.

Aged↗
PubMed2004

Three-dimensional (3-D) reconstruction of the spine from a single X-ray image and prior vertebra models.

The lateral bending test is routinely used by clinicians for the preoperative assessment of spinal mobility. The evaluation of bending motion is usually based on the qualitative analysis of a two-dimensional (2-D) antero-posterior X-ray image. The aim of this paper is to introduce a novel three-dimensional (3-D) reconstruction technique that is a prerequisite for the quantitative 3-D analysis of lateral bending motion. An algorithm was developed for the 3-D reconstruction of the spine from a single X-ray image. The X-ray is calibrated using a small calibration object and an explicit calibration algorithm. The information contained in the single X-ray is completed by registering a priori 3-D geometric models of individual vertebrae. Part of the error yielded by the 3-D/2-D registration is corrected by a vertebral alignment constraint that aims to minimize intervertebral dislocations. Three-dimensional models of 15 different scoliosis patients, obtained from a standard stereo-radiographic 3-D reconstruction, were used in simulation and validation experiments. Experimental results show that the new method is robust and accurate. With pessimistic levels of simulated noise, the average root mean square reconstruction error is 2.89 mm, which is appropriate for common clinical applications.

Algorithms↗
PubMed2003

Boston brace correction in idiopathic scoliosis: a biomechanical study.

STUDY DESIGN: To analyze Boston brace biomechanics, pressure measurements and finite element simulations were done on 12 adolescent idiopathic scoliosis patients. OBJECTIVES: The aim was to analyze the Boston brace effectiveness using a finite element model and experimental measurements. SUMMARY OF BACKGROUND DATA: There are not very many biomechanical studies of Boston brace effectiveness, and its biomechanical action is not completely understood. METHODS: This study was performed on 12 girls with scoliosis treated with the Boston brace system. The experimental protocol was composed of the acquisition of two sets of multiplanar radiographs with and without brace followed by the pressure acquisition at the brace-torso interface. A personalized finite element modeling of the trunk was generated from the 3D reconstruction of the patient's geometry. The brace treatment was simulated by the application of equivalent forces calculated from the pressure measurements. RESULTS: Two Boston brace force patterns were defined from the pressure measurements. The first one consisted of high right thoracic forces of 31-113 N, lumbar forces less than 47 N, and included a left thoracic extension working as a counter pad. The second one consisted of low thoracic forces less than 20 N, lumbar forces up to 70 N, without left thoracic extension. The simulations showed that the passive forces only produced a coronal Cobb angle correction up to 9 degrees, whereas real correction was up to 16 degrees. CONCLUSION: High thoracic pads reduced more effectively both thoracic and lumbar scoliotic curves than lumbar pads only. The study suggests that mechanisms other than brace pads produce correction and contribute to the force equilibrium within the brace.

Adolescent↗
PubMed2003

Sagittal plane analysis of the spine and pelvis in adolescent idiopathic scoliosis according to the coronal curve type.

STUDY DESIGN: A retrospective study investigated the sagittal alignment in adolescent idiopathic scoliosis (AIS). OBJECTIVE: To evaluate the sagittal alignment of the spine and pelvis in adolescent idiopathic scoliosis on the basis of curve type. SUMMARY OF BACKGROUND DATA: The relation between the spine and pelvis highly influences the sagittal balance in adults. However, the sagittal alignment of the spine and pelvis in adolescent idiopathic scoliosis is poorly defined in the literature. METHODS: Five sagittal parameters were evaluated on lateral radiographs of 160 patients with adolescent idiopathic scoliosis: thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence. The patients were classified according to their coronal curve type. Analysis of variance was used to compare the parameters between the curve types, and Pearson coefficients were used to investigate the relation between all parameters (alpha = 0.05). RESULTS: The thoracic kyphosis was significantly lower for King I, II, and III curves than for lumbar curves. The lumbar lordosis was higher for lumbar curves, although not significantly. No significant change between the groups was observed for the sacral slope, pelvic tilt, or pelvic incidence. The pelvic incidence was significantly correlated with the lumbar lordosis, sacral slope, and pelvic tilt for all the groups. The lumbar lordosis was strongly related to the sacral slope in all cases, but not with the thoracic kyphosis, except in the case of thoracolumbar curves. CONCLUSIONS: Thoracic kyphosis depended mostly on the spinal deformity, whereas lumbar lordosis was influenced mainly by the pelvic configuration. The scoliotic curve type was not associated with a specific pattern of sagittal pelvic morphology and balance. The pelvic incidence found in this study was significantly higher than that reported in the literature for normal adolescents. The role of the pelvic incidence in the pathogenesis of adolescent idiopathic scoliosis needs to be explored in a longitudinal study involving patients with adolescent idiopathic scoliosis and normal adolescents.

Adolescent↗